The attack in Manaus, capital of the northern state of Amazonas, took place on August 17, 2010, just outside the victim's house, lead prosecutor Joao Bosco Valente said.

But the case didn't come to light until the video was broadcast by several television stations on Wednesday night.

The boy's family, the man who shot the video, and a reporter who first saw the footage, did not report the alleged crime for fear of retaliation from the police, Mr Valente said.

The victim's family was so afraid it moved to a different neighbourhood, he said. The videographer finally released the video to TV stations.

Police in Manaus did not immediately return calls for comment.

In the soundless footage, five police officers are seen forming a semi-circle around the slight teenager and backing him up against the wall of his own home.

The officers start pushing the boy around, eventually taking close-range shots at him as he scoots along the wall.

He is seen sinking down to the ground as the officers try to lead him away.

Although it can't be heard, the boy's mother began screaming for help in the background when she found out what was happening, Mr Valente said.

The prosecutor said the officers allegedly involved in the shooting told him they were asking the minor about a gun used in a crime in the neighbourhood.

Mr Valente did not say if they gave an explanation for why they began to shoot the teen. He added that the boy had no criminal record.

The boy was hit five times, Mr Valente said. He spent 10 days in a hospital, according to the prosecutor's spokeswoman, Cristina Magda Pereira Goes.

One of the shots punctured his lung, requiring him to spend two days in the intensive care unit, Ms Pereira said. "He didn't die because of sheer luck," she said.

No details of his other injuries were released. Authorities also withheld the minor's name and the names of the officers, who have not yet been charged.

The boy and his family have been put in a witness-protection program, Mr Valente said.

"They only felt safe when they were entered into the program, and were told the officers would be detained," he said. "What these officers did was barbaric. They completely ignored the basic task of police, which is to protect the public."